This is an overall view of my furnace. As you can see it is made from a steel garbage can. The air blower on the left was taken out of a dishwasher and the heating element was removed (all done by me of course) and I built a simple wood frame to support it.
This is a look at the inside of the furnace. The internal dimensions are 10 inches wide and 18 inches tall. Now this is where the furnace really gets interesting. There is no fireclay nor castable refractory used in the entire furnace! Although you can't tell by the picture (because of all the ash) the inner chamber is made from a terra-cotta clay chimney pipe! I simply cut one in half and centered it in the garbage can. Then I filled the gap between the chimney pipe and the garbage can with regular cement! Will this method last? I've been using this furnace heavily for over a year and it doesn't need any repair! Remember you learned it here first! At the The Lab!
This is a look at the furnace fully loaded with charcoal briquettes and the crucible nestled in the center ready to be fired up!
Now, I know some of you are wondering; "What about the lid?" Oh yes! The lid too is made from regular cement reinforced with steel wires and crushed pieces of regular bricks. Now you'll probably look at the picture and say; "Whoa! That lid has seen better days." True, but the large chunk that broke off is not a result of the heat. The lid broke when the furnace fell off the cart one day in my haste to melt metal. It smashed onto the driveway. Indeed that was a sad day for the foundry and I. But amazingly it still works well.